feat: allow symmetrization of down variations

[alexander-held]

Template symmetrization was previously only possible for up variations (meaning the down variation is created via symmetrization). This update also enables symmetrization for down variations.

* allow symmetrization of down variations to create templates for up variations
* updated pre-commit

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (2baf8f5) to head (b84439b).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #470 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 22 22 Lines 2083 2093 +10 Branches 340 344 +4 ========================================= + Hits 2083 2093 +10 ```

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